The invention relates to a brake pad for a disc brake, in particular for a utility or commercial vehicle, having a pad retaining spring.
A brake pad of this type is known from WO 2007/068464 A1. Such a brake pad has been proven in principle, with significant advantages being the improved safety with regard to the non-reusability of the pad retaining spring and an improvement in the spring characteristic. Also cited as prior art are DE 40 20 287 A1, EP 232 303 B1, U.S. Pat. No. 5,064,028 A, U.S. Pat. No. 4,784,242 A and U.S. Pat. No. 4,049,087 A.
For optimum spring behavior, the pad retaining spring must have a corresponding width which is greater than the thickness of the lining carrier plate, such that the pad retaining spring projects at least at one side beyond the lining carrier plate.
To fasten a hood to the lining carrier plate, one of the two parallel limbs of the hood, which, in one section, is bent into a U-shape, engages in a positively locking manner into the lining carrier plate. To guide the two limbs as close as possible to the associated sides of the lining carrier plate, it is necessary for the pad retaining spring to be cut out in the region in which the hood engages over, to such an extent that, there, the pad retaining spring corresponds in terms of its width approximately to the thickness of the lining carrier plate. That is to say, the pad retaining spring is narrower in the region of overlap with the hood than in the region of the spring limbs which adjoin at both sides.
As has been proven, in the cut-out region, there is under some circumstances the risk of fatigue failure, since the pad retaining spring, on account of its function, undergoes frequent radial deflections, that is to say load cycles.
A desired optimized service life of the brake pad naturally opposes this situation, with an exchange of the brake pad solely for this reason leading to considerably increased costs, which result from the production of a new brake pad, the assembly and disassembly costs, and the costs for the vehicle being in a non-operational state.
The invention provides a brake pad wherein with little design and production expenditure, its service life, in particular that of its pad retaining spring, is increased.
In particular, a brake pad for a disc brake includes a pad retaining spring which is designed as an arc-shaped leaf spring, can deflect radially and is fastened by use of a hood to a lining carrier plate supporting a friction lining material. The hood is formed as a separate component and has a section which is U-shaped in cross-section. A web of the hood, which connects the limbs guided in parallel at both sides of the lining carrier plate, bears against the pad retaining spring. The pad retaining spring has an opening through which one limb of the hood is guided.
It is therefore now possible for the pad retaining spring to be designed so as to have, preferably, a constant width. This, first of all, advantageously results in a required and satisfactory fatigue strength even in the region of overlap with the hood, and secondly, allows the spring characteristic to remain unchanged to a defined and desired extent substantially over the entire length of the pad retaining spring. In other words, variations due to material weakening are substantially prevented.
According to one advantageous refinement of the invention, the opening, which is provided in the pad retaining spring, is designed as a longitudinal slot whose width corresponds approximately to the thickness of the metal sheet from which the hood is produced. Its length corresponds approximately to the width of the hood in the penetrated region. In this respect, the pad retaining spring is also secured against a longitudinal displacement.
According to another advantageous refinement of the invention, after being mounted on, that is to say after being fastened to, the lining carrier plate, the U-shaped section of the hood is shaped, by way of a connecting web which runs parallel to the web which bears against the pad retaining spring, so as to form a peripherally closed structure, wherein the free end of the connecting web can be cohesively connected to the associated limb, preferably by means of welding. It is, however, also possible to provide a positive locking connection, with interlocking positive-locking devices then being provided on the limb, on the one hand, and on the connecting web, on the other hand.
For the leadthrough of the connecting web, the lining carrier plate has a passage opening, which is dimensioned such that a longitudinal displacement of the pad retaining spring (and of the hood which is fastened thereto) is substantially prevented, while a radial movement is easily possible, corresponding to the spring stroke.
For this purpose, a rectangular or square opening can be provided in the lining carrier plate, which opening, if the lining carrier plate is cast, is concomitantly cast during the casting process, or which opening, if the lining carrier plate is composed of a sheet-metal molded part, is punched-in.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.